Honestly? It depends on the relationship the two of you have and the personalities you have and God knows what else. If you want it explicit, you have to say explicitly how much time you think that is.

It depends on the situation. If I tell a friend that I’m in class and I’ll text them in a bit, it’ll be after class. If I’m eating dinner, it’ll be after dinner. If there’s no specific reason why they can’t talk about whatever it is right now, I’d guess a bit would be a few hours at most.